From: "Jan Beulich" <JBeulich@suse.com>
To: Juergen Gross <jgross@suse.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Wei Liu <wei.liu2@citrix.com>,
xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [for-4.9] Re: HVM guest performance regression
Date: Tue, 30 May 2017 09:10:44 -0600 [thread overview]
Message-ID: <592DA794020000780015DBFB@prv-mh.provo.novell.com> (raw)
In-Reply-To: <41b3b844-9ab6-be69-b7ea-df9073ecba26@suse.com>
>>> On 30.05.17 at 16:57, <jgross@suse.com> wrote:
> On 30/05/17 12:43, Jan Beulich wrote:
>>>>> On 30.05.17 at 12:33, <jgross@suse.com> wrote:
>>> On 30/05/17 09:24, Jan Beulich wrote:
>>>> But if the OS allocated large pages internally for relevant data
>>>> structures, those obviously won't come from that necessarily 4k-
>>>> mapped tail range.
>>>
>>> Sure? I think the kernel is using 1GB pages if possible for direct
>>> kernel mappings of the physical memory. It doesn't care for the last
>>> page mapping some space not populated.
>>
>> Are you sure? I would very much hope for Linux to not establish
>> mappings to addresses where no memory (and no MMIO) resides.
>> But I can't tell for sure for recent Linux versions; I do know in the
>> old days they were quite careful there.
>
> Looking at phys_pud_init() they are happily using 1GB pages until they
> have all memory mapped.
It's the layers higher up which I think make sure to call this with
bit PG_LEVEL_1G set only when covering all RAM (see
split_mem_range()).
Jan
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next prev parent reply other threads:[~2017-05-30 15:10 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-26 16:14 HVM guest performance regression Juergen Gross
2017-05-26 16:19 ` [for-4.9] " Ian Jackson
2017-05-26 17:00 ` Juergen Gross
2017-05-26 19:01 ` Stefano Stabellini
2017-05-29 19:05 ` Juergen Gross
2017-05-30 7:24 ` Jan Beulich
[not found] ` <592D3A3A020000780015D787@suse.com>
2017-05-30 10:33 ` Juergen Gross
2017-05-30 10:43 ` Jan Beulich
[not found] ` <592D68DC020000780015D919@suse.com>
2017-05-30 14:57 ` Juergen Gross
2017-05-30 15:10 ` Jan Beulich [this message]
2017-06-06 13:44 ` Juergen Gross
2017-06-06 16:39 ` Stefano Stabellini
2017-06-06 19:00 ` Juergen Gross
2017-06-06 19:08 ` Stefano Stabellini
2017-06-07 6:55 ` Juergen Gross
2017-06-07 18:19 ` Stefano Stabellini
2017-06-08 9:37 ` Juergen Gross
2017-06-08 18:09 ` Stefano Stabellini
2017-06-08 18:28 ` Juergen Gross
2017-06-08 21:00 ` Dario Faggioli
2017-06-11 2:27 ` Konrad Rzeszutek Wilk
2017-06-12 5:48 ` Solved: " Juergen Gross
2017-06-12 7:35 ` Andrew Cooper
2017-06-12 7:47 ` Juergen Gross
2017-06-12 8:30 ` Andrew Cooper
2017-05-26 17:04 ` Dario Faggioli
2017-05-26 17:25 ` Juergen Gross
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